In recent years, Low-power and Lossy Wireless Networks (LLWNs) have become a very important and challenging topic. LLWNs consist of spatially distributed autonomous devices which have limited energy, memory and processing resources. Applications for such networks may range, for instance, from environment monitoring (e.g. wireless sensor networks), to consumer electronics applications (e.g. remote control systems), to health monitoring (e.g. wireless devices worn on one's person for monitoring vital signs such as heart rates), to lighting control (e.g. for intelligent building management).
In many applications over LLWNs, it is required to control several nodes at the same time. For instance, lighting networks have the specific requirement that many lights need to be switched on, off or dimmed almost simultaneously. In LLWNs where packet technologies are used, such as Internet Protocol (IP), multicast transmission is the proper choice for such applications. Indeed, with multicast, information is communicated from a single source to a group of destinations (e.g., one or more nodes).
However, it has been found that such combination (e.g. IP+Multicast) over LLWNs appears to suffer from high end-to-end delays when the load of the traffic increases. Hence, high delays may be perceived by an end user from the moment where a control command is triggered till the moment where the command is actually executed at desired location within the network. This is problematic and it would be preferable to have the possibility to minimise end-to-end delays in LLWNs when network traffic load increases.